Evidence-based Laboratory Medicine: Finding and Assessing the Evidence

Transcription

1 Find Assess Decide Evidence-based Laboratory Medicine: Finding and Assessing the Evidence Pieter Vermeersch, M.D. Ph.D. Laboratory Medicine, UZ Leuven November 18th 2008

2 Introduction Archie Cochrane ( ) Professor of Medicine (University of Cardiff) Effectiveness and Efficiency: Random Reflections on Health Services (1972) McMaster University (Canada) Current methodologies to determine "best evidence" were largely established in the 1980s by the McMaster University research group led by David Sackett and Gordon Guyatt Evidence-based medicine The term first appeared in medical literature in 1992 in a paper by Guyatt et al.

3 Introduction What is Evidence Based-Medicine? Evidence-based medicine is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients. Sackett DL, Rosenberg WM, Gray JA, Haynes RB, and Richardson WS. "Evidence based medicine: what it is and what it isn't". BMJ 1996;312:71 2

4 Introduction What is Evidence Based-Medicine? Evidence-based medicine is the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients. Sackett DL, Rosenberg WM, Gray JA, Haynes RB, and Richardson WS. "Evidence based medicine: what it is and what it isn't". BMJ 1996;312:71 2 How keep up with new developments in medicine? 1) Information from pharmaceutical/diagnostic industry 2) Continuing education (symposia, conferences) 3) Grazing through the medical literature Time consuming

5 Introduction Avalanche of Information of varying quality 2007: articles tracked in PubMed => > pages/day => >1 km/year => > kg/year Journal associated score of personal angst J: Are you ambivalent about renewing your JOURNAL subscriptions? A: Do you feel ANGER towards prolific authors? S: Do you ever use journals to help you SLEEP? P: Are you surrounded by PILES of PERIODICALS? A: Do you feel ANXIOUS when journals arrive? From BMJ 1995;311: => Need for a strategy to find and assess evidence

6 Finding and assessing the Evidence Evidence-based Medicine Steps 1) Define answerable Question 2) Search 3) Appraise 4) Decide Systematic review Steps 1) Define answerable Question 2) Search ) Appraise x2 4) Synthetize 5) Apply Quick and Dirty Time: 1 hour < 10 articles This patient survives! Time: 6 months >100 articles This patient is dead Find a systematic review!!

7 Define an Answerable Question PICO-model Population (patient/condition) How would you describe a group of patients similar to yours? What are the most important characteristics of the patient? Intervention (drug, procedure, diagnostic test, exposure) Which main intervention, prognostic factor, or exposure are you considering? What do you want to do for the patient? Prescribe a drug? Order a test? Comparison What is the main alternative to compare with the intervention? Are you trying to decide between two drugs? Two diagnostic tests? Outcome What can you hope to accomplish, measure, improve or affect? What are you trying to do for the patient? Relieve or eliminate the symptoms?

8 Finding the Evidence Define answerable Question Search for systematic reviews (Cochrane SR, DARE, PubMed) Yes Assess quality

9 Finding the Evidence Meta-analysis Systematic review Meta-analysis - The statistical technique involved in extracting and combining data to produce a summary result. - Meta-analysis is a two-step process Step 1: Extraction of data from each individual study and the calculation of the result and confidence interval for each study. Step 2: Deciding whether it is appropriate to calculate a pooled average result across studies and, if so, calculating and presenting such a result. A greater weight can be given to studies which give us more information, because these are likely to be closer to the truth we are trying to estimate. Systematic Review - The entire process of collecting, reviewing and presenting all available evidence Metaanalysis Systematic Review

10 Finding the Evidence Meta-analysis Systematic review Meta-analysis - The statistical technique involved in extracting and combining data to produce a summary result. - Meta-analysis is a two-step process Step 1: Extraction of data from each individual study and the calculation of the result and confidence interval for each study. Step 2: Deciding whether it is appropriate to calculate a pooled average result across studies and, if so, calculating and presenting such a result. A greater weight can be given to studies which give us more information, because these are likely to be closer to the truth we are trying to estimate. Systematic Review - The entire process of collecting, reviewing and presenting all available evidence Metaanalysis Systematic Review

11 Assessing the Evidence Avoiding bias - Evidence-based medicine ranks evidence in different categories according to the strength of the evidence. The strength reflects to what extend the results are free from the various biases that affect medical research. - Important sources of bias include: 1) Author conflict of interest 2) Publication bias 3) Confounding variable => may create an apparent association or mask a real association

12 Assessing the Evidence Avoiding bias - Evidence-based medicine ranks evidence in different categories according to the strength of the evidence. The strength reflects to what extend the results are free from the various biases that affect medical research. - Important sources of bias include: 1) Author conflict of interest 2) Publication bias 3) Confounding variable => may create an apparent association or mask a real association Qualification of evidence - The strongest evidence for therapeutic interventions is provided by systematic review of randomized, double-blind, placebo-controlled trials involving a homogeneous patient population and medical condition. - Patient case reports and expert opinion have little value as proof because of the placebo effect, the biases inherent in observation and reporting of cases, difficulties in ascertaining who is an expert, etc. - Different systems to stratify evidence by quality have been developed.

13 Levels of Evidence Level 1a Therapy/Prevention, Aetiology/Harm Systematic review (with homogeneity*) of Randomized controlled trials (RCT) Prognosis Diagnosis Differential diagnosis/symptom prevalence study SR (with homogeneity*) of inception cohort studies; CDR validated in different populations SR (with homogeneity*) of Level 1 diagnostic studies; CDR with 1b studies from different clinical centres Validating** cohort study with good reference standards; or CDR tested within one clinical centre SR (with homogeneity*) of prospective cohort studies Economic and decision analyses SR (with homogeneity*) of Level 1 economic studies 2a 2b Oxford Centre for Evidence-based Medicine Levels of Evidence (May 2001) Systematic review (with homogeneity*) of cohort studies Individual cohort study (including low quality RCT; e.g., <80% follow-up) SR (with homogeneity*) of either retrospective cohort studies or untreated control groups in RCTs Retrospective cohort study or follow-up of untreated control patients in an RCT; Derivation of CDR or validated on splitsample only SR (with homogeneity*) of Level >2 diagnostic studies Exploratory** cohort study with good reference standards; CDR after derivation, or validated only on split-sample or databases SR (with homogeneity*) of 2b and better studies Retrospective cohort study, or poor follow-up 1b Individual RCT (with narrow confidence interval) Individual inception cohort study with > 80% follow-up; CDR validated in a single population Prospective cohort study with good follow-up**** Analysis based on clinically sensible costs or alternatives; systematic review(s) of the evidence; and including multi-way sensitivity analyses 1c All or none All or none case-series Absolute SpPins and SnNouts All or none case-series Absolute better-value or worsevalue analyses SR (with homogeneity*) of Level >2 economic studies Analysis based on clinically sensible costs or alternatives; limited review(s) of the evidence, or single studies; and including multi-way sensitivity analyses 2c "Outcomes" Research; Ecological studies "Outcomes" Research Ecological studies Audit or outcomes research 3a SR (with homogeneity*) of casecontrol studies SR (with homogeneity*) of 3b and better studies SR (with homogeneity*) of 3b and better studies SR (with homogeneity*) of 3b and better studies 3b Individual Case-Control Study Non-consecutive study; or without consistently applied reference standards Non-consecutive cohort study, or very limited population Analysis based on limited alternatives or costs, poor quality estimates of data, but including sensitivity analyses incorporating clinically sensible variations. 4 Case-series (and poor quality cohort and case-control studies ) Case-series (and poor quality prognostic cohort studies***) Case-control study, poor or nonindependent reference standard Case-series or superseded reference standards Analysis with no sensitivity analysis 5 Expert opinion without explicit critical appraisal, or based on physiology, bench research or "first principles" Expert opinion without explicit critical appraisal, or based on physiology, bench research or "first principles" Expert opinion without explicit critical appraisal, or based on physiology, bench research or "first principles" Expert opinion without explicit critical appraisal, or based on physiology, bench research or "first principles" Expert opinion without explicit critical appraisal, or based on economic theory or "first principles"

14 Levels of Evidence Oxford Centre for Evidence-based Medicine Levels of Evidence (May 2001) Level 1a 1b 1c 2a Therapy Systematic review of randomized controlled trials (RCT) Individual randomized controlled trial (with narrow confidence interval) All patients died before treatment was available OR some died before treatment was available, but none now with treatment Systematic review of cohort studies 2b Individual cohort study (including low quality RCT; e.g., <80% follow-up) 2c 3a 3b Ecological studies (comparison of different populations) Systematic review of case-control studies Individual Case-Control Study 4 Case-series (and poor quality cohort and case-control studies) 5 Expert opinion without explicit critical appraisal, or based on physiology, bench research or "first principles"

15 Levels of Evidence Oxford Centre for Evidence-based Medicine Levels of Evidence (May 2001) Level 1a 1b 1c 2a 2b 3a 3b Diagnosis SR (with homogeneity) of Level 1 diagnostic studies OR CDR validated with 1b studies from different clinical centers Validating cohort study with good reference standards OR CDR tested within one clinical centre Specificity so high that positive result rules in the diagnosis OR Sensitivity so high that negative result rules out the diagnosis SR (with homogeneity) of Level 2 and better diagnostic studies Exploratory cohort study with good reference standards OR CDR after derivation or validated only on databases SR(with homogeneity) of 3b and better studies Non-consecutive study OR study without consistently applied reference standards 4 Case-control study OR study with poor or non-independent reference standard 5 Expert opinion without explicit critical appraisal, or based on physiology, bench research or "first principles" CDR: clinical decision rule; SR: systematic review

16 Grades of Recommendations Oxford Centre for Evidence-based Medicine Levels of Evidence Level A - Consistent level 1 studies - clinical decision rule validated in different populations Level B - Consistent level 2 or 3 studies OR - extrapolations from level A studies Level C - Case-series study OR - extrapolations from level B studies Level D - Expert opinion without explicit critical appraisal OR - based on physiology, bench research or first principles

17 The Cochrane Collaboration The Cochrane collaboration ( - An international not-for-profit and independent organization, dedicated to making up-to-date, accurate information about the effects of healthcare readily available worldwide. - The goal is to produce and disseminate systematic reviews of healthcare interventions and promote the search for evidence in the form of clinical trials and other studies of interventions. - Cochrane reviews in the Cochrane Database of Systematic Reviews(CDSR) answer clinical questions about the effectiveness of treatments (medications, surgery, education, etc). + Relies on grants and donations, and doesn't take conflicted funding + At least 2 independent authors review the evidence - No free access in belgium (individual license $285). - Only a limited number of topics have been dealt with - Only limited interest in diagnostic tests (same for other similar initiatives)

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25 The Cochrane Library The Cochrane Library contains 6 databases 1) The Cochrane Database of Systematic Reviews (CDSR) 2) Database of Abstracts of Reviews of Effectiveness (DARE) 3) The Cochrane Central Register of Controlled Trials (CENTRAL) 4) The Cochrane Methodology Register (CRM) 5) Health Technology Assessment Database (HTA) 6) The NHS Economic Evaluation Database (NHS EED)

26 The Cochrane Library The Cochrane Library contains 6 databases 1) The Cochrane Database of Systematic Reviews (CDSR) 2) Database of Abstracts of Reviews of Effectiveness (DARE) 3) The Cochrane Central Register of Controlled Trials (CENTRAL) 4) The Cochrane Methodology Register (CRM) 5) Health Technology Assessment Database (HTA) 6) The NHS Economic Evaluation Database (NHS EED)

27 The Cochrane Library The Cochrane Library contains 6 databases 1) The Cochrane Database of Systematic Reviews (CDSR) 2) Database of Abstracts of Reviews of Effectiveness (DARE) 3) The Cochrane Central Register of Controlled Trials (CENTRAL) 4) The Cochrane Methodology Register (CRM) 5) Health Technology Assessment Database (HTA) 6) The NHS Economic Evaluation Database (NHS EED)

28 The Cochrane Library Centre for Reviews and Dissemination (CDR) - The Centre for Reviews and Dissemination (CDR) is a department of the University of York and a part of the U.K. National Institute for Health Research. - CRD undertakes systematic reviews that evaluate the effects of health and social care interventions and the delivery and organisation of health care. - Results are added to the DARE, NHS EED and HTA databases. - The DARE database contains structured abstracts commenting on published reviews.

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30 => Review is ongoing

31 Clear objective = OK No inclusion criteria defined = not good No reference standard defined = not good Patient group clearly defined = OK

32 Publication bias not assessed No criteria defined = not good Statistical methods described = OK Heterogeneity discussed = OK

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34 Other Value-added Databases American College of Physicians Journal Club - Articles that report original studies and systematic reviews that warrant immediate attention by physicians attempting to keep pace with important advances in internal medicine are summarized in value-added abstracts and commented on by clinical experts. - All abstracts can be accessed free of charge. - Also focuses on diagnostic studies BMJ Clinical Evidence - Summarizes information therapeutic trials - No focus on diagnostic tests

35 Finding the Evidence Define answerable Question Search for systematic reviews (Cochrane SR, DARE, PubMed) Yes Assess quality No Search for controlled trials (Cochrane CENTRAL Register, PubMed) Yes Assess evidence No You are entering territory with lower quality evidence

36 PubMed - Developed by the U.S. National Institutes of Health (NIH). - Indexing works via Medical Subject Headings (MeSH). - All abstracts can be accessed free of charge. - Some articles can be accessed free of charge, either because the journal provides free online access or because the authors paid an additional fee to make their article freely available (required by some funding organizations). - Special plug-in allows you to indentify the articles that can be accessed via the biomedical library from the K.U.Leuven.

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38 PubMed Optimizing your PubMed search 1) Check for relevant MeSH terms 2) Combine MeSH terms and free text with Boolean operators (CAPITALS) e.g. hypertension AND beta-blocker e.g. sildenafil NOT erectile dysfunction e.g. (myocardial NEXT infarction) OR (acute NEAR ischemia) 3) Restrict search e.g. only reviews e.g. only articles in English 4) Specify criteria e.g. Hill, S. [Au] e.g. Hypertension [MeSH] 5) Search via clinical queries

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42 PubMed Optimizing your PubMed search 1) Check for relevant MeSH terms 2) Combine MeSH terms and free text with Boolean operators (CAPITALS) e.g. hypertension AND beta-blocker e.g. troponin AND (myocardial infarction OR acute coronary syndrome) e.g. sildenafil NOT erectile dysfunction 3) Define limits e.g. only reviews e.g. only articles in English 4) Specify criteria e.g. Hill, S. [Au] e.g. Hypertension [MeSH] 5) Search via clinical queries

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44 PubMed Optimizing your PubMed search 1) Check for relevant MeSH terms 2) Combine MeSH terms and free text with Boolean operators (CAPITALS) e.g. hypertension AND beta-blocker e.g. troponin AND (myocardial infarction OR acute coronary syndrome) e.g. sildenafil NOT erectile dysfunction 3) Define limits e.g. only reviews e.g. only articles in English 4) Specify criteria e.g. Hill, S. [Au] e.g. Hypertension [MeSH] 5) Search via clinical queries

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47 PubMed Optimizing your PubMed search 1) Check for relevant MeSH terms 2) Combine MeSH terms and free text with Boolean operators (CAPITALS) e.g. hypertension AND beta-blocker e.g. troponin AND (myocardial infarction OR acute coronary syndrome) e.g. sildenafil NOT erectile dysfunction 3) Define limits e.g. only reviews e.g. only articles in English 4) Specify criteria e.g. Hill, S. [Au] e.g. Hypertension [MeSH] 5) Search via clinical queries

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49 PubMed Optimizing your PubMed search 1) Check for relevant MeSH terms 2) Combine MeSH terms and free text with Boolean operators (CAPITALS) e.g. hypertension AND beta-blocker e.g. troponin AND (myocardial infarction OR acute coronary syndrome) e.g. sildenafil NOT erectile dysfunction 3) Define limits e.g. only reviews e.g. only articles in English 4) Specify criteria e.g. Hill, S. [Au] e.g. Hypertension [MeSH] 5) Search via clinical queries

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52 Finding the Evidence Define answerable Question Clinical practice guidelines Search for systematic reviews (Cochrane SR, DARE, PubMed) Yes Assess quality No Assess evidence Search for controlled trials (Cochrane CENTRAL Register, PubMed) Yes Assess evidence No You are entering territory with lower quality evidence

53 Clinical Practice Guidelines AGREE (appraisal of guidelines research and evaluation) - International collaboration of researchers and policy makers who seek to improve the quality and effectiveness of clinical practice guidelines - shared framework for their development, reporting and assessment. - Funded by BIOMED-2 program of European Union National Guideline Clearinghouse - Public resource for evidence-based clinical practice guidelines.

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62 SUMSearch SUMSearch - Searches Cochare Library, DARE, NGC and PubMed.

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70 Find Assess Decide Questions?